Electric reaction furnace



Oct. 29, 1940. BERGHAUS -r AL 2,219,612

ELECTRIC REACTION FURNACE Filed July I4. 1938 a Sheets-Sheet 1 B B 1* haus w. u lha fi Ina/anions Oct. 29, 1940. B. BERGHAUS ET AL ELECTRIC REACTION FURNACE Filed July 14, 1938 3 Sheets-Sheet 2 1 .6 9 A 5 4 5 w 15; 4 u #4 a 0 5 \\\\N\ x 7 N Q w I 61 m 4 m u a e Q p m Oct. 29, 1940. s, BERGHAU Er AL 2,219,612

ELECTRIC REACTION FURNACE Filed July 14, 1938 3 Sheets-Sheet 3 Patented o'er. 1940 I um'rso STATES TEN OFFICE ELECTRIC nEAc'rIoN FURNACE.

Bernhard Berghaus, Berlin-Innkwitz, and Wilhelm Burkhardt, Berlin-Grunewald, Germany; said Burkhardt assignor to said Berghaus Application July-14, 193:, Serial in. 219,294

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This invention relates to an annealing or melting furnace operating under reduced pressure. and pertains to an arrangement wherein the conducting crucible in which the annealing or melt- 1 5 ing material is accommodated is heated in a nieerably completely. The pressure may amount to 40 to 0.001 and preferably to 0.01 millimeters of mercury.

When the crucible is heated by a direct current voltage applied tothe path of discharge, the crucible is connectedto the negative terminal of the source of voltage and the vacuum vessel may.

carry the positive voltage. Preferably, one or more electrodes arranged within the housing are connected to the positive pole of the direct,cur-

rent voltage. This arrangement hasthe advan tage that the vessel does-not carry any dangerous voltages during the operation. The crucible is mounted on one or more supports introduced in an insulated and vacuum-tight manner. One or all the supports may take over the conduction ofthe current to the negative pole of the source of voltage. Neutral supportsmay consist of insulat-- 80 mg material such as porcelain, quartz or other v sintered bodies. The supports and the conductors are hollow and their inner walls are cooled. Water, oil or compressed air may be used as the cooling means. The cooling of the conductors is 315 necessary in order to prevent the insulation and v sealing material provided between the conductor and the vessel or thescreen from being burnt. The cooling of the conductor or of the supports is effected along such a length that no substan- 40 tial drop in temperature occurs at the points of contact with the crucible. A thermo-element for measuring the temperature is introduced through one of the supponts in a vacuum-tightmanner. In order toobtain an exact temperature measurement the thermo-element projects into the cru-v cible. In order to protect the thermo-element it. is preferably surrounded by the wall of the crucible. .Use may be made also of only one support which serves at the sametime as a conductor and as a support for the thermo-element.

' When the crucible is heated by an alternating current voltage applied to the path of discharge one or' more electrodes are connected with one terminal of the source and the crucible with the other terminal of the alternating current voltage.

ermany August 26, 1937 7 Claims. (Ci. 13- 31) The invention is illustrated diagrammatically and by way of example in the accompanying drawings, inwhich: I

v 'Figure 1 is asection through an annealing and melting furnace working at reduced pressure with a melting crucible for heating by glow current; Figure 2 is a plan view of the three supports for the melting crucible according to Figure 1;-

, Figure 3 is a middle sole supp rt of the melting crucible on an enlarged scale 1 V Figure 4 is a diagram of connections for direct current operation and Figure 5 is a diagram of connections for alternating current operation.

In Fig. 1, which shows a section through an annealing and melting furnace l for operation at reduced pressure provided with a crucible 2 filled with melting material for heating with a glow current, the crucible 2 is supported on three metal supports 5, 6, T mounted in the vessel 4; I

The housing is closed in. a vacuum-tight manner by a cover 3, and the supports serve at the same time to supply the negative voltage to the crucible. These supports and current leads are introduced in an insulated manner into the vacuum vessel 4 and are screened by metallic sleeves 8. Current is supplied to the supports by means of cables 9 and the parts I0, H and the clamping ring i2 consist of insulating material, the insulator H completely covers a flange [8 of the current lead which maybe made hollow and be cooled by air so that no disturbing additional discharges take place. The supports of the crucible carry cap members l5 to prevent impurities from falling into the space between the current leads and the sleeves. The crucible 2 is provided with a recess in which a thermo-element I1 is mounted which is introduced into the vacuum vessel 4 similarly insulated and screened by a sleeve to. The outer or connecting ends of the thermo-element are indicated at II and a metallic screening sleeve or tubular member I! surrounds the vthermo-element. The tubular member i8 and the screening. sleeve in are insulated and sealed with respect to the housing- 4 by insulating rings 20 and I I.

The vacuum vessel 4 'is provided-with a jacket 22 to which a cooling medium such as water or oil is supplied through the pipe connection 23, being discharged through'the pipe connection 2 4. A pipe connection for a vacuum pump is shown at 25. Indifferent or reducing gases such as. hydrocarbons may be supplied by the pipe connection 2!. The cover {of the vacuum vessel is provided with a Jacket "as well aswith ll 2 pipe connections 29 and 8B for the supply and discharge-of the cooling medium. An inspection hole is illustrated at 3! provided with a vacuum tight window. A packing ring 82 is provided bee tween the housing 4 and the cover 3 and clamps 33 tion.

In Fig. 3 only one support 34 carries the crucible 2. Thesupport is at the same time a curare arranged for securing the cover in posi- 10 rent lead and support for the thermo-element H. The support 34 is hollow and the cooling medium may be introduced through the pipe 35 and discharged through the pipe connection 86. The insulating ring 37 covers the flange 88 of the licurrenit lead completely. An insulating ring 39 is provided for clamping the flange 38 imposition by means of bolts 6!. The insulating ring or disk it is'sealed with respect to the housing 5 by means of a soft metal ring it. Likewise the 20 flange 38 is sealed with respect to the insulating disk 3? by means of a soft metal ring M.

One of the metal screens in Fig. 3 is formed of two sleeves at and Alta, The upper sleeve i l is removable so as to beexchanged without removing the lower sleeve tlia. The other screen is formed by a sleeve 65 which surrounds the sleeve 45a in a spaced relation to provide an annular space therebetween. The sleeve Ma carries a cap member 62 for preventing dirt from falling into the annular space between the sleeve 45 and the sleeve 44a. Another cap member 33 is provided for preventing foreign particles from entering the annular space between the conductor 34 and the sleeve 46. The upper end of the conductor as engages the crucible in a recess era.

connected to the crucible by A diagram of connections for heating'the crucible Z by direct current is shown in Fig. 4. A source of direct current is provided by a gener'ator 4B and a negative terminal 88 thereof is the cables 9 in Fig. 1

or the wire 42 in Fig. 3. e positive terminal said openings, a conducting crucible for receiving material to be heated arranged within said housing engaging ends of said conductors so as to be supported within thevessel in a spaced relation with respect to the housing, means insulating and sealing said conductors with respect of the generator may be connected to the housing 4 by means of a circuit which includes. a resistor 41 and a switch 48. The positive terminal may also be connected to auxiliary electrodes I50 and BI arranged'within the housing by means of a circuit'which includes the resistor 41 and a switch 49. v

A circuit arrangement for heating the crucible by means of alternating current is illustrated in Fig. wherein one terminal of a secondary winding 52 of a transformer is adapted to be connected to the crucible 2 through a switch 53. The other terminal of the secondary 62 is connected 55 to the auxiliary electrodes 50 and BI 60 parts or sealings.

The screening. has the advantage that largeelectrical energies can be introduced in a reliable -manner into the vacuum vessel in the case of a glow discharge, withoutdamaging the insulating The advantages of the glow current heatingreside in the fact that the electrical energy is' released directly at the material of the crucible, the crucible material thus acting as a heating element, whereby a favourable trans-' mission of heat with good efllciency' is obtained.

The walls'of the vacuum chamber which may be cooled or heat-insulated are maintained at such a temperature that they are capable of withstanding the atmospheric'pressure.

.What we claim is: a

1. In a gas discharge heating or annealing furnace', a separable sealed metal housing providing a vacuum vessel, the lower portion of said housing having a plurality of openings therein, a rigid con uctor extending upwardly through each of cible having a recess in the to said housing, a screening sleeve surrounding each of said conductors in a spaced relation adjacent said housing to provide an annular space between each sleeve and the respective conductor, and a cap member associated with each conductor for preventing impurities from passing downwardly into the annular spaces.

.2. In a gas discharge heating or annealing furnace, a separable sealed metal housing providing a vacuum vessel, the lower portion of said housing having a plurality of openings therein, a rigid conductor extending upwardly through each 01' said openings, a conducting crucible for receiving material to be heated arranged within said. housing engaging ends of said conductors so as to be supported within the vessel in a spaced relation with respect to the housing, means insulating and sealing said conductors with respect to said housing, said crucible having a recess I therein, a tubular member extending through an rial to be heated arranged within said housing engaging the ends of saidconductors so as to be supported within saidvessel in a spaced relation with respect to the housing, means arranged outside the vessel insulating and sealing said conductors with respect to the housing, and a screening sleeve surrounding each of said conductors in a spaced relation adjacent said housing to provide an annular space between each sleeve and the respective conductor.

4. In an electric reaction furnace, a separable sealed metal housing providing an evacuable ves-' sel, the lower portion of said housing having an opening therein, a crucible for receiving mate rial to be heated supported within said housing in a spaced relation said crucible having a recess therein, a thermoelement extending through the opening in said housing and into said recess, a tubular member surrounding said thermo-element and extending-- through said opening into sulating and sealing said respect to said housing, anda screening sleeve surrounding said tubular member in a spaced relation adjacent saidhousing to provide an annular space between the sleeve and said tubular member.

5. In an electric reaction furnace, a separable sealed metal housing providing an evacuable vessel, the lower portion of said said recess, means inwardly through said opening, a conducting crulower portion thereof, to receive material to said crucible being adapted with respect to the housing,

tubular member with.

housing having an opening therein, a rigidconductor extending upbe heated and arranged within said-housing engaging the end of said conductor within said recess so as to be supported on the rigid conductor in a spaced relation wlthrespect to the housing, means arranged outside the vessel for insulatlng and sealing said conductor with respect to said housing, and a screening sleeve surroimding said conductor in a spaced relation adjacent said housing to provide an annular space between said sleeve and the conductor.

6. In an electric reaction furnace, a separable sealed metal housingproviding an evacuable vessel, the lower portion of. said housing having a plurality of openings therein, a rigid conductor extending upwardly through each of said openin'gs,-a conducting crucible for receiving material to be heated arranged within said housing engaging the ends of said conductors so as to be supported within said, vessel in a spaced relation with respect to the housing, means arranged outside the vessel insulating and sealing said conductors with respect to the housing, a screening sleeve surrounding each or said conductors in a spaced relation adjacent said housing to provide an annular space between each sleeve andthe respective conductor, each conductor being solid adjacent said crucible and hollow adjacent said housing for receiving a cooling medium to cool the'conductors adjacent the insulating and sealing means without substantially affecting the temperature'ofthe conductors adjacent the crucible. a

'7. In an electric reaction furnace, a separable sealed metal housing providing an evacuable vessel, the lower portion of said housing having an opening therein, a rigid conductor extending upwardly through said opening, a conducting crucible having a recess in the lower portion thereof, said crucible being adapted to receive material to be heated and arranged within said housing engaging the end of said conductor within said recess so asto be supported in a spaced re: lation with respect to the housing, means insulating and sealing said conductor with respect to said housing, a screening sleeve surrounding said conductor in a spaced relation adjacent said housing to provide an annular space 'between said sleeve and the conductor, a thermo-element extending through said conductor terminating in said recess, said conductor being hollowadjacent said housing, and means for introducing a cooling medium into the hollow portion 01' said conductor for cooling the same adjacent the insulating and sealing means without any substantial cooling of the conductor adjacent the crucible. 

